Cell corrosion reduction

Abstract

Corrosion is reduced in aqueous electrochemical cells having zinc anodes comprised of single crystal zinc particles by the addition of small amounts of a gas inhibiting surfactant, for example, an organic phosphate inhibitor such as RA600 from GAF Corp. to the cell. A synergistically lowered rate of corrosion and cell gassing is obtained even with reduction of mercury content.

What is claimed is: 
     
       1. An electrochemical cell subject to reduced gassing comprising an anode, a cathode, and an alkaline electrolyte characterized in that said anode is comprised of single crystal zinc anode metal particles wherein said particles comprise up to about 1.5% by weight mercury and said cell includes a surface active hetero polar additive having a polar affinity to said anode. 
     
     
       2. The cell of claim 1 wherein said additive is present in said anode in an amount ranging between 0.001% to 5% by weight thereof. 
     
     
       3. The cell of claim 1 wherein said surface active hetero polar material additive is selected from the group consisting of ethylene oxide containing polymers, monocarboxylic acid with at least two ethanolamide groupings, tridecyloxypoly(ethylenoxy) ethanol, and organic phosphate esters. 
     
     
       4. The cell of claim 3 wherein said anode includes a metal gas inhibitor selected from the group consisting of indium, thallium, gallium, bismuth, cadmium, tin, lead, and mixtures thereof, wherein each metal-gas inhibitor present is in an amount of 25-5000 ppm, and wherein said zinc particles comprise up to about 0.5% by weight mercury. 
     
     
       5. The cell of claim 4 wherein said surface active hetero polar material additive is an organic phosphate ester having the formula: ##STR2## where x+y=3 M=H, ammonia, amino, or an alkali or alkaline earth metal and   R=phenyl or alkyl or alkylaryl of 6-28 carbon atoms.   
     
     
       6. The cell of claim 5 wherein said organic phosphate ester is comprised of a member of the group consisting of the free acid of an anionic organic phosphate ester based on a linear primary alcohol, and being an unneutralized partial ester of phosphoric acid; the free acid of an anionic complex organic phosphate ester having an aromatic hydrophobe, and being an unneutralized partial ester of phosphoric acid; and an anionic mono substituted ortho phosphate ester. 
     
     
       7. The cell of claim 6 wherein said organic phosphate ester is comprised of the free acid of an anionic organic phosphate ester based on a linear primary alcohol, and being an unneutralized partial ester of phosphoric acid. 
     
     
       8. The cell of claim 7 wherein said organic phosphate ester is present in said anode in amounts ranging between 0.005% to 1% by weight thereof. 
     
     
       9. The cell of claim 8 wherein each metal gas inhibitor present is in an amount of 100-1000 ppm. 
     
     
       10. An electrochemical cell comprising an anode, a cathode and an aqueous alkaline electrolyte characterized in that said anode is comprised of zinc particles with up to 0.5% mercury and a metal gas inhibitor selected from the group consisting of indium, thallium, gallium, bismuth, cadmium, tin, lead and mixtures thereof and each metal gas inhibitor present is in an amount between 100 and 1000 ppm; and wherein said cell further comprises a surface active organic phosphate ester additive having a polar affinity to said anode and said organic phosphate ester additive is present in an amount between .005% and 1% by weight thereof. 
     
     
       11. The cell of claim 10 wherein said metal gas inhibitors are indium and lead. 
     
     
       12. An electrochemical cell subject to reduced gassing comprising an aqueous alkaline electrolyte, a cathode and an anode comprised of mercury amalgamated single crystal zinc particles and an organic phosphate ester with said mercury comprising up to about 1.5% by weight of said anode and said organic phosphate ester being comprised of the free acid of an anionic organic phosphate ester based on a linear primary alcohol, and being an unneutralized partial ester of phosphoric acid with said organic phosphate ester comprising from 0.01 to 0.3% by weight of said anode. 
     
     
       13. The cell of claim 12 wherein said cathode is comprised of manganese dioxide and said aqueous electrolyte is comprised of a potassium hydroxide solution.